1. Field of the Invention
The present invention relates to a detection apparatus that illuminates a sample and detects light reflected by the sample.
2. Description of the Related Art
In measurement of the reflection characteristic of a sample, an optical condition for illumination and observation, called geometry, greatly affects the measurement result, so a geometry suited to a sample is adopted. For example, 45/0 geometry (45° illumination-vertical light receiving) is employed when measuring a printed product. Since directional illumination is done for such geometries, an illumination apparatus is required to illuminate a measurement sample with light from a specific direction (Japanese Patent Laid-Open No. 2008-286530). Japanese Patent Laid-Open No. 2008-286530 proposes an illumination apparatus for two 45° directions.
However, a conventional directional illumination system has difficulty in obtaining high illuminance distribution uniformity while illuminating a sample from all directions. If the number of illumination directions is small, accurate measurement fails under the influence of the installation direction of a sample, rotation, or the like. When the entire measurement region cannot be illuminated with a uniform illuminance distribution, no accurate measurement can be done under strong influence of a portion having high illuminance in the measurement region. As a method of uniforming the illuminance distribution while implementing omni-directional illumination, a method using an integrating sphere, and the like are known. However, the use of the integrating sphere decreases the efficiency of light use.